The aim of this proposal is to gain a deeper understanding of the frequency and geographic distribution of single nucleotide substitutions discovered in our set of 94 individuals of dispersed ethnic background in the coding, regulatory and flanking intronic sequences of various genes. The genes will be chosen t random, utilizing data generated at the Stanford DNA Sequencing and Technology Center as part of the NIH sponsored initiative of large-scale discovery of single nucleotide polymorphisms (1-R01-HG01932-01). At the present production level, we will discover as many as 5,000 new simple sequence polymorphisms in approximately 150 genes per year. Single nucleotide polymorphisms discovered in more than one continent or with a frequency > 10% in a single continent will be genotyped by multiplex single nucleotide extension sequencing reactions followed by HPLC analysis, utilizing the same primers and conditions already established for their discovery. For this purpose, we will screen 50 additional individuals form the same ethnic group of geographic region to establish whether the allele is indeed unique or relatively common in a particular population. Information on the frequency and geographic distribution of single nucleotide polymorphisms is considered valuable for understanding gene histories, particularly with regard to selection. In collaboration with the other participants in this program project we will test existing as well as device new algorithms to test the neutral evolution hypothesis.